U.S. patent application number 11/075094 was filed with the patent office on 2006-09-14 for led mounting having increased heat dissipation.
Invention is credited to Thye Linn Mok, Shin Wen Ng, Siew Kim Tan.
Application Number | 20060202210 11/075094 |
Document ID | / |
Family ID | 36241161 |
Filed Date | 2006-09-14 |
United States Patent
Application |
20060202210 |
Kind Code |
A1 |
Mok; Thye Linn ; et
al. |
September 14, 2006 |
LED mounting having increased heat dissipation
Abstract
There is disclosed a system and method for increasing heat
dissipation of LED displays by using the current PCB packaging
mounted to a LCD panel support structure thereby eliminating the
need for a metal core PCB. In one embodiment, reverse mounted LEDs
having heat dissipation pads are used to optimize heat transfer to
a metal layer which is then placed in contact with the LCD support
structure.
Inventors: |
Mok; Thye Linn; (Bukit
Mertajam, MY) ; Tan; Siew Kim; (Alor Setar, MY)
; Ng; Shin Wen; (Bukit Mertajam, MY) |
Correspondence
Address: |
AGILENT TECHNOLOGIES INC.;INTELLECTUAL PROPERTY ADMINISTRATION, LEGAL
DEPT,
M/S DU404
P.O. BOX 7599
LOVELAND
CO
80537-0599
US
|
Family ID: |
36241161 |
Appl. No.: |
11/075094 |
Filed: |
March 8, 2005 |
Current U.S.
Class: |
257/79 ; 257/622;
257/623; 257/98; 257/E25.02; 257/E33.056; 257/E33.058; 257/E33.059;
257/E33.075; 438/106; 438/110; 438/126; 438/25 |
Current CPC
Class: |
H01L 2224/73265
20130101; H01L 33/642 20130101; H01L 33/647 20130101; H01L
2224/48091 20130101; H01L 2924/00014 20130101; H01L 33/54 20130101;
H01L 2224/48091 20130101 |
Class at
Publication: |
257/079 ;
257/098; 257/622; 257/623; 438/025; 438/106; 438/110; 438/126;
257/E33.058 |
International
Class: |
H01L 21/00 20060101
H01L021/00; H01L 33/00 20060101 H01L033/00; H01L 21/50 20060101
H01L021/50; H01L 29/06 20060101 H01L029/06 |
Claims
1. An LED assembly comprising: a substrate having a heat-sink pad
forming a bottom surface thereof, an LED mounted at least partially
on said substrate and having a portion of said LED physically
bonded to the heat sink pad; and wire bond pads on a top surface of
said substrate, said wire bond pads electrically connected to said
LED.
2. The assembly of claim 1 further comprising: a reflector cup
constructed within said substrate, said LED positioned within said
reflector cup.
3. The assembly of claim 2 wherein said portion of said LED in
contact with said heat-sink pad is a portion designed for the
dissipation of heat from said LED.
4. The assembly of claim 2 further comprising: an optical dome
covering said LED and said reflector cup.
5. The assembly of claim 4 wherein said optical dome is part of a
substrate positioned to cover said top surface.
6. The assembly of claim 3 further comprising: a separate substrate
positioned over said substrate, said separate substrate having
electrical contacts for making electrical contact with at least a
portion of said wire bond pads; and wherein said separate substrate
has constructed therein provision for allowing light from said LED
to be visible to an observer.
7. The assembly of claim 6 further comprising: a support structure
connected to said heat-sink pad.
8. The assembly of claim 7 wherein said PCB substrate contains a
plurality of said LEDs all in contact with said heat-sink and
wherein said heat-sink is in contact with said support
structure.
9. The assembly of claim 8 wherein said separate substrate has
constructed therein provision allowing light from said plurality of
LEDs to be visible to an observer.
10. An array of LEDs, said array comprising: a first substrate
having reflector cups constructed therein, said reflector cups for
mounting said LEDs therein; said first substrate having attached
thereto a heat conducting layer in physical contact with a first
surface of mounted ones of said LEDs; said first substrate
comprising: electrical pads for connecting to mounted ones of said
LEDs, said electrical pads positioned so as to communicate
electrical control signals from a mating substrate, said mating
substrate having constructed therein control circuitry for
controlling said LEDs; said LED array further comprising: a heat
conducting support structure in non-electrical contact with said
heat conducting layer so as to transfer away heat generate from the
operation of mounted ones of said LEDs.
11. The array of claim 10 wherein said mating substrate comprises:
a plurality of optical domes for allowing light from mounted ones
of said LEDs to be radiated away from said mating substrate, said
light radiating from a second surface of said LEDs.
12. The array of claim 10 wherein said heat conducting layer is a
metal layer.
13. The array of claim 10 wherein said heat conducting support
structure is a metal structure.
14. The array of claim 10 wherein said heat conducting support
structure is mated to said heat conducting layer with a thermally
conductive, non-electrically conductive dielectric.
15. A method of constructing an LED array, said method comprising:
constructing in a first substrate a reflector area for mounting an
LED therein, said reflector area containing a heat transfer
material in contact with a bottom surface of said first substrate;
and constructing on a top surface of said first substrate contact
pads for connecting with electrical contacts of a mounted LED, said
contact pads also having area for making electrical contact with
electrical contacts on a second substrate in contact with said top
surface of said first substrate; positioning said LED within said
reflector area with a bottom surface of said LED that is physically
bonded to said heat transfer material.
16. (canceled)
17. The method of claim 16 further comprising: positioning a light
dome over said reflector area to disperse light from a mounted
LED.
18. The method of claim 17 further comprising: constructing a
plurality of said reflector areas of said first substrate.
19. The method of claim 18 further comprising: mounting a plurality
of said first substrates, each with a plurality of reflector areas
upon a support structure to form a matrix array of LEDs.
20. The method of claim 17 further comprising: mounting a plurality
of said first substrates on a support structure to form an array of
LEDs, said array being controlled from said second substrate.
Description
BACKGROUND OF THE INVENTION
[0001] The need for LEDs having high power (increased brightness)
is increasing. As power increases, so does the need for heat
dissipation since if the heat generated by the LED junction is not
dissipated effectively the brightness of the LED is diminished.
[0002] Currently LEDs are produced in surface-mounted LED packages
which are mounted to aluminum metal core PCBs. The metal core PCBs
act as direct heat-sinks drawing the heat away from the LEDs. Using
metal core PCBs is relatively expensive since the cost of the
material for a metal core PCB is high.
BRIEF SUMMARY OF THE INVENTION
[0003] There is disclosed a system and method for increasing heat
dissipation of LED displays by using the current PCB packaging
mounted to a LCD panel support structure thereby eliminating the
need for a metal core PCB. In one embodiment, reverse mounted LEDs
having heat dissipation pads are used to optimize heat transfer to
a metal layer which is then placed in contact with the LCD support
structure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] For a more complete understanding of the present invention,
reference is now made to the following descriptions taken in
conjunction with the accompanying drawing, in which:
[0005] FIG. 1 shows a perspective view of one embodiment of a
single LED and dome package;
[0006] FIG. 2 shows one embodiment of the LED package of FIG. 1
with the LED removed;
[0007] FIGS. 3A and 3B show embodiments of side views of the single
LED package of FIG. 1 taken along section line 3A-3A of FIG. 2;
[0008] FIGS. 4 and 5 show top and side views, respectively, of a
multiple LED package; and
[0009] FIGS. 6 and 7 show a display using LED strips constructed in
accordance with the teachings of this disclosure.
DETAILED DESCRIPTION OF THE INVENTION
[0010] FIG. 1 shows a perspective view of one embodiment of single
LED package 10 consisting of PCB substrate 22 mated to heat-sink
pad 25. Optical dome 12 is constructed, by molding or otherwise,
above surface 11 which in turn is mated to substrate 22. Contact
strips 23 and 24 are constructed on the surface of substrate 22 and
are used as discussed in more detail hereinafter.
[0011] FIG. 2 shows package 10 with the LED and optical dome 12
removed. An LED chip (or other light emitting source) would be
physically attached to heat-sink pad 25 inside reflector cup 21 by
a terminally conductive bonding agent, or by other fastener means.
The LED would then be wire bond connected to pads 23-1 and 24-1 of
contact strips 23 and 24, respectively, for subsequent connection
to an external electrical path. The heat path from the LED is
through heat-sink pad 25 which can be, for example, copper. Note
that the heat path from the LED is pad 25 and is separate from the
electrical path to optimize the heat dissipation from the die to
the back structure. The LED is mounted to pad 25 using a thermally
conductive (but non-electrically conductive) adhesive dielectric.
The heat dissipation is better than in prior art metal core PCBs
because the pad has a wider surface area.
[0012] Reflector cup 21 is constructed having an optimum angle for
reflecting LED side light to the top of the package. The reflector
cup is formed, for example, using bright color opaque material.
Once the LED is mated with pad 25, transparent material is poured
around the LED to encapsulate the LED and wire bond to form
complete LED package 10.
[0013] Optical dome 12 (FIG. 1) is constructed to direct the light
from the LED source in a desired direction. The light output of the
LED can be changed, as desired, to applications simply by
redesigning the dome shape.
[0014] FIG. 3A shows a sectional cut-away side view of LED package
10 taken along section line 3A-3A of FIG. 2 having light source,
such as LED 31, physically bonded to heat dissipation pad 25 by
bonding material 302. Bond wire 32 connects one terminal of LED 31
to contact pad 24-1 of contact strip 24 (FIG. 1). The second
electrical terminal of LED 31 is connected to contact pad 23-1 by
path 33. Any electrical contact system can be used to connect LED
31 to respective contacts external to dome 12. In the embodiment
shown, there are two such leads but there could be three or more,
if desired.
[0015] FIG. 3B shows in a cut-away view how external power is
connected via contacts 52 and 53 to contact area 23-2 and 24-2. The
position of contact areas 23-1, 23-2, 24-1, and 24-2 is shown in
FIG. 2. Note that these contacts can be any place along contact
strip 23, 24 so long as they do not interfere with the wire bonds
to the LED. FIG. 4 shows display 40 having a plurality of LED
packages 10-1 through 10-N, each with an LED 12-1 to 12-N.
Surrounding each LED package is a opening, such as opening 42-1
through 42-N formed in structure 42 to allow light from the
respective LED to pass through.
[0016] FIG. 5 is a cross-section of display 40 taken a long line
5-5 of FIG. 4 showing three LEDs 12-1, 12-2, 12-3 mounted to
mounting plate 61. (Mounting plate 61 will be described more fully
with respect to FIG. 6.) Shown in FIG. 5 are contacts 52 and 53
which are formed beneath the surface of structure 41 for the
purpose of providing control and power to the respective LEDs. This
then allows for the contact surface to be on the top side of the
LED device and away from heat pad 25 for better electrical and heat
separation.
[0017] FIG. 6 shows system 60 which has a plurality of LED strips
40 mounted to heat dissipation bar 63 which in turn is connected to
back mounting plate 61. If desired, cover 62 can be added. Cover 62
could have opaque areas for allowing the LED light to be seen
externally.
[0018] FIG. 7 shows a cross-section of structure 60 taken along
section line 7-7 of FIG. 6. In FIG. 7 light diffusers and other
elements 72, 73 are shown for diffusing, or otherwise controlling
the light. Such control can be on an individual basis, if
desired.
[0019] FIG. 8 shows one alternate embodiment 80 of a device using
light source 92 having both bond wires on the top of the light
source. This is possible because of the horizontal structure of
light source 92 as shown in FIG. 9B. In this embodiment adhesive
(or other bonding agent) 802 can be both heat conductive as well as
electrically conductive. This then allows for the use of solder as
the bonding agent which could, in some situations, be more
effective than simply being heat conductive.
[0020] FIG. 9A shows a diagram of vertical structure light source
91 having its electrical connections at the top and at the bottom
of the device.
[0021] FIG. 9B shows a diagram of horizontal structure light source
92 having both its electrical connections at the top of the device.
Note that while only two electrical connections are shown, any
number can be used and the concepts discussed herein could work
with conductors coming from the sides of the device if desired.
[0022] Although the present invention and its advantages have been
described in detail, it should be understood that various changes,
substitutions and alterations can be made herein without departing
from the spirit and scope of the invention as defined by the
appended claims. Moreover, the scope of the present application is
not intended to be limited to the particular embodiments of the
process, machine, manufacture, composition of matter, means,
methods and steps described in the specification. As one of
ordinary skill in the art will readily appreciate from the
disclosure of the present invention, processes, machines,
manufacture, compositions of matter, means, methods, or steps,
presently existing or later to be developed that perform
substantially the same function or achieve substantially the same
result as the corresponding embodiments described herein may be
utilized according to the present invention. Accordingly, the
appended claims are intended to include within their scope such
processes, machines, manufacture, compositions of matter, means,
methods, or steps.
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